Experimental and numerical investigations of aluminum foam-filled auxetic circular tubular metamaterials with elliptical cells

Aluminum foam-filled circular auxetic metamaterials were designed, fabricated and investigated in this work. Firstly, the mechanical properties and deformation modes of the proposed aluminum foam-filled auxetic tubes (AFFAT) were analyzed using experimental and finite numerical methods. The load capacity of the AFFAT is larger than the sum of the load for the auxetic tube and aluminum foam. Secondly, the effect of aluminum foam's density on the mechanical properties of AFFAT was studied. The results show that the energy contribution ratio of the interaction between the aluminum foam and auxetic tube improves with the aluminum foam's density. Then, the effect of unit cell size on the mechanical properties of AFFAT was investigated. It can be concluded that the compression load efficiency of AFFAT with the ratio of the elliptical major axis to the minor axis increases. Finally, the study of tube type's effect on the mechanical properties of AFFAT was carried out. Among the investigated composite structures, the AFFAT has the highest compression load efficiency. Due to their unique structural design and excellent mechanical properties, the AFFAT has great potential for applications in aero-space, vehicle crashworthiness and protective infrastructure.